With the switch in one position, the signals from the rear O2 sensors will be fed into the DME for normal driving. With the switch in the other position, the simulated signal from the DP Fix will be fed into the DME for inspection time.

Extract the wires from the DME connector as described in the DP Fix instructions. *Make a note of which yellow wire goes to pin 19.* You can wrap a tape "flag" around this wire temporarily.

Figure out where you want your switch and drill a hole in the white box (1/4"). I mounted mine on the front side of the box, near the outside so I can reach it with the cowl cover in place.

Cut off the two female terminals on the black wires of the DP fix. Leave equal lengths of wire on the DP Fix and the terminal ends. The two wires with the female terminals will connect to the center terminals of the switch and to the DME. The two ends of the black wires from the DP fix will connect to the bottom terminals of the switch. Add 12 inches to each of the wires (4) and cover the splices with shrink tubing.

Cut a "window" in the insulation for the black wire with a male terminal on the DP Fix. Use your wire strippers to cut the insulation in two places about 1/4" apart. CAREFULLY use a sharp knife to slit the cut section of insulation so that it may be removed from the wire. Solder the end of 12 inches of wire to this window. Slide shrink tube over the splice.

Solder one of the extra male terminals you bought to the end of 12 inches of black wire. Carefully use pliers to clamp down each side of the insulation barrel over the insulation of the wire.

Place the DP Fix in the white box, and route all wires to allow for neat installation. Refer to the schematic for guidance. Run the wires that go to the switch through the 1/4" hole to judge how long they need to be. Once all wires are neat and in place, cut off the excess hanging outside the box through the hole.

Solder the wires which attach to the DME pins 19 and 20 to the center terminals of the switch on each side. Ensure you place shrink tube over the wire BEFORE you solder it. Slide the shrink tube over the switch terminals and shrink it. *Make sure you know which side goes to pin 19.*

Solder the black wires from the DP fix to the bottom terminal of the switch. Apply shrink tube as directed above.

Solder the end of the black wire connected to the male terminal of the DP fix to the side of the switch which is connected the pin 19 on the DME. Apply shrink tubing.

Solder the other black wire with the male terminal to the other side of the switch. Apply shrink tubing.

Install the switch and boot in the hole.

Slide shrink tube over the black wire of the DP fix with the male terminal. Insert the male terminal into the female terminal on the yellow wire which you removed from pin 19 on the DME connector. Shrink the tubing over the connection to secure and insulate it.

Repeat step 12 for the other black wire with a male terminal and the other yellow wire which was removed from position 20.

Insert the black wires with female terminals into the DME connector. Ensure the proper wire is inserted into position 19.

Follow the DP fix instructions for the red wires.

Notes:

Practice makes perfect when heating shrink tubing with a lighter. Just get the flame close, it does not have to actually touch the tubing. You could use a heat gun if you prefer.

The switch has six terminals. Holding the switch so that there are three terminals on the right, and three terminals on the left, each side is one circuit independent from the other. With the level in the up position, the center terminals on each side are connected to the bottom terminals on each side. With the lever down, the center terminals on each side are connected to the top terminals on each side. The terminals on the left are never connected to the terminals on the right.

If a wire crosses another in the schematic and there is NO DOT, the wires are NOT CONNECTED. Dots indicate wire which are connected.

You only really need one male terminal, but buy five or ten of each in case you need to correct a mistake.

If at some point you connect the wrong O2 sensor to the wrong input on the DME, you will throw a code. Pay attention to which sensor connects to pin 19, and the other must connect to pin 20.

The coffee was extra strong this morning so I may have overlooked something in my caffeine induced ADHD frenzy.

It seems difficult to get the housings, though. I've read somewhere that they were only originally distributed to BMW. On some of the Tyco drawings there is a note that says the drawing cannot be changed without getting approval from BMW first.

It seems difficult to get the housings, though. I've read somewhere that they were only originally distributed to BMW. On some of the Tyco drawings there is a note that says the drawing cannot be changed without getting approval from BMW first.

The goal is to allow you to switch between the rear O2 sensor signals going to the correct pins on the DME, or routing the simulated DP Fix signal to those two pins. Because you are dealing with two inputs on the DME, and two sources of the signal for each DME pin you need a double pole double throw switch. This is the most elegant way I could think to do it, but it surely is not the only way to solve the problem.

I still think you might be able to get there with a simplified circuit. If you used a DPST to short the DPFix input to the output, that might be the same as cutting the DPFix out of the circuit (assuming the DPFix isn't a load meaningful load in that config).

Interesting. What kind of symptoms are people having from running the dpfix all the time? I've had mine in for a few months since I've been tuneless. I haven't really noticed anything, but I haven't been monitoring anything either.

As I understand it, the way the car monitors catalyst operation is by comparing the pre and post catalyst sensor data. During cruising, the pre catalyst senor will fluctuate around and lambda of 1. Some times above, sometime below. The three way catalyst has the ability to store oxygen, so it acts as a buffer. What you see at the rear sensor is fluctuation, but only about 25 or 50% as often. It's the slower fluctuation of the rear sensor that the DME uses to gauge the functionality of the catalyst.

With race downpipes, you remove the catalysts, thereby causing both the front and rear sensor to fluctuate at the same rate. What the DP Fix does is take the fluctuations of only one rear sensor and divides it, sending the resulting signal to both rear sensor inputs.

Innovate is fairly clear on their site that factors like age and altitude can make the Bosch wideband sensors inaccurate. Their LC-1 wideband system uses free air calibration to periodically reset the sensor's calibration and keep it accurate despite changing conditions. Obviously BMW does not expect the owner or the service department to do periodic free air calibrations of the two wideband sensors. The work around is using data from the rear sensor to keep the front wideband in check.

As noted above, the DP Fix takes the output of one sensor, divides it, and sends the signal to both sensor inputs on the DME. What happens is the DME never gets the proper rear sensor signal from one of the sensors. It gets the signal from the other banks's sensor. The fact that the signal has been divided is of no consequence because it is averaged over time. So what the DME does is apply corrections to Bank 2 wideband based on data from Bank 1 rear sensor. Obviously these corrections are erroneous.

As you can image, acting on erroneous data the Bank 2 sensor can no longer give an accurate reading. So you may see a divergence in lambda between banks because the closed loop control of the second bank is functioning with an inaccurate sensor, as it has had the wrong calibration applied to it. Or maybe you won't see the divergence, because the sensor is reading one thing, but the actual lambda is something different.

Of course this is somewhat of a theory because no one has the source code for the DME. However, BMS does not recommend the DP Fix be left on the car for precisely this reason. I believe it was @themyst that was having mixture problems originally and it was traced back to the DP Fix with Terry's help.

As I understand it, the way the car monitors catalyst operation is by comparing the pre and post catalyst sensor data. During cruising, the pre catalyst senor will fluctuate around and lambda of 1. Some times above, sometime below. The three way catalyst has the ability to store oxygen, so it acts as a buffer. What you see at the rear sensor is fluctuation, but only about 25 or 50% as often. It's the slower fluctuation of the rear sensor that the DME uses to gauge the functionality of the catalyst.

With race downpipes, you remove the catalysts, thereby causing both the front and rear sensor to fluctuate at the same rate. What the DP Fix does is take the fluctuations of only one rear sensor and divides it, sending the resulting signal to both rear sensor inputs.

Innovate is fairly clear on their site that factors like age and altitude can make the Bosch wideband sensors inaccurate. Their LC-1 wideband system uses free air calibration to periodically reset the sensor's calibration and keep it accurate despite changing conditions. Obviously BMW does not expect the owner or the service department to do periodic free air calibrations of the two wideband sensors. The work around is using data from the rear sensor to keep the front wideband in check.

As noted above, the DP Fix takes the output of one sensor, divides it, and sends the signal to both sensor inputs on the DME. What happens is the DME never gets the proper rear sensor signal from one of the sensors. It gets the signal from the other banks's sensor. The fact that the signal has been divided is of no consequence because it is averaged over time. So what the DME does is apply corrections to Bank 2 wideband based on data from Bank 1 rear sensor. Obviously these corrections are erroneous.

As you can image, acting on erroneous data the Bank 2 sensor can no longer give an accurate reading. So you may see a divergence in lambda between banks because the closed loop control of the second bank is functioning with an inaccurate sensor, as it has had the wrong calibration applied to it. Or maybe you won't see the divergence, because the sensor is reading one thing, but the actual lambda is something different.

Of course this is somewhat of a theory because no one has the source code for the DME. However, BMS does not recommend the DP Fix be left on the car for precisely this reason. I believe it was @themyst that was having mixture problems originally and it was traced back to the DP Fix with Terry's help.

Great explanation, would be nice to know for sure what is really going on in the code, but does sound like the safest thing to do is live with the CEL.

I wish terry would make a super cheap JB that just did auto code clearing and gauge sweeps because I like my GIAC stage 2, but would like to not have to look at the CEL without the DPFix (and the gauge sweep is just cool!)

Great explanation, would be nice to know for sure what is really going on in the code, but does sound like the safest thing to do is live with the CEL.

I wish terry would make a super cheap JB that just did auto code clearing and gauge sweeps because I like my GIAC stage 2, but would like to not have to look at the CEL without the DPFix (and the gauge sweep is just cool!)

ROb

So Terry emailed me and they make their CANTool which is exactly what I need for under 200 bucks, will auto clear my codes and give me the gauge sweep (new a couple weeks ago) a shift light and some other gauge hijack stuff - basically all the JB4 can features without the tune since I am flashed and does it through the OBDII port, so you don't even have to wire it in.

Ordered one and will be pulling the DPFix and only using it when I need it!

As I understand it, the way the car monitors catalyst operation is by comparing the pre and post catalyst sensor data. During cruising, the pre catalyst senor will fluctuate around and lambda of 1. Some times above, sometime below. The three way catalyst has the ability to store oxygen, so it acts as a buffer. What you see at the rear sensor is fluctuation, but only about 25 or 50% as often. It's the slower fluctuation of the rear sensor that the DME uses to gauge the functionality of the catalyst.

With race downpipes, you remove the catalysts, thereby causing both the front and rear sensor to fluctuate at the same rate. What the DP Fix does is take the fluctuations of only one rear sensor and divides it, sending the resulting signal to both rear sensor inputs.

Innovate is fairly clear on their site that factors like age and altitude can make the Bosch wideband sensors inaccurate. Their LC-1 wideband system uses free air calibration to periodically reset the sensor's calibration and keep it accurate despite changing conditions. Obviously BMW does not expect the owner or the service department to do periodic free air calibrations of the two wideband sensors. The work around is using data from the rear sensor to keep the front wideband in check.

As noted above, the DP Fix takes the output of one sensor, divides it, and sends the signal to both sensor inputs on the DME. What happens is the DME never gets the proper rear sensor signal from one of the sensors. It gets the signal from the other banks's sensor. The fact that the signal has been divided is of no consequence because it is averaged over time. So what the DME does is apply corrections to Bank 2 wideband based on data from Bank 1 rear sensor. Obviously these corrections are erroneous.

As you can image, acting on erroneous data the Bank 2 sensor can no longer give an accurate reading. So you may see a divergence in lambda between banks because the closed loop control of the second bank is functioning with an inaccurate sensor, as it has had the wrong calibration applied to it. Or maybe you won't see the divergence, because the sensor is reading one thing, but the actual lambda is something different.

Of course this is somewhat of a theory because no one has the source code for the DME. However, BMS does not recommend the DP Fix be left on the car for precisely this reason. I believe it was @themyst that was having mixture problems originally and it was traced back to the DP Fix with Terry's help.

The DP fix caused AFR imbalances between banks when I was running Cobb, but the fuel mixture codes were attributed to a bum O2 sensor. Probably got fouled when I blew the seal in my RBs and they were spewing wet oil out my exhaust.